As will be appreciated herein below, except as otherwise indicated, aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2011 and are well known to the person skilled in the art.
For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated. The term “up to” and “up to about”, as employed herein, explicitly includes, but is not limited to, the possibility of zero weight-percent of the particular alloying component to which it refers. For example, up to about 0.2% Ti may include an alloy having no Ti.
Self-piercing riveting (“SPR”) is a well-established technique for joining together components such as, for example, sheet metal. A self-piercing rivet typically comprises a head and a partially hollow cylindrical shank that terminates in an annular piercing edge and is inserted into one or more sheets of material. The rivet is driven by a punch of a setting tool into the sheets such that the shank pierces through the upper sheet (or sheets) and flares outwardly whilst supported by a die. It is inserted without full penetration such that the deformed end of the rivet remains encapsulated by an upset annulus of the material thus forming a mechanical interlock. Self-piercing riveting enables sheet material to be joined without the requirement for the pre-drilling or pre-punching of a hole in the material.
Self-piercing riveting technology has application in many manufacturing industries but has been particularly successful in the automotive industry where there is a drive to use material of lighter weight without reducing safety. SPR has been used to join components such as aluminium vehicle body panels, which cannot be spot-welded easily. SPR techniques have proven to be successful in this context not only because they produce joints of good strength and fatigue properties that can be easily automated on a production line but also because the joints are aesthetically acceptable in that there is little distortion of the upper surface of the sheet material around the rivet.
Riveting, and SPR in particular, is faced with increasing challenges in terms of the types of joints that manufacturers would like to produce using this technology, in particular when using high-strength aluminium series alloys such as those of the AA7000-series alloys.